Plastic watt-hour meter base



Jan. 16, 1945. ROAD 2,367,433

PLASTIC WATT-HOUR METERBASE Filed July 8, 1941 4 Sheets-Sheet 1 r--/4 I 54 /a Z ATTORNEYS.

Jan. 16, 1945.

R. A. ROAD PLASTIC WATT-HOUR METER BASE Filed July 8, 1941 4 Sheets-Sheet 2 INVENTOR.

BY M7 ATTORNEYS.

Jan. 16, 1945. R. A. ROAD PLASTIC WATT-HOUR METER BASE Filed July 8, 1941 4 Sheets-Sheet 5 heretofore.

latcntecl Jan. E6. 1945 PLASTIC WATT-HOUR METER BASE Richard A. Road, La Fayette, Ind, asslgnor to Duncan Electric Manufacturing Company, La Fayette, Ind, a corporation of Illinois Application July 8, 1941, Serial No. 401,444

l3 @laims.

In bases for watt-hour meters there are a number of features that are extremely desirable. They should fit standard covers and connecting facilities since interchangeability is important commercially. The cover should seal tightly against the base so that dust and water cannot enter the meter chamber. Preferably, it should be very difficult to drill a hole through the base, particularly into the meter chamber, through which a wire may be inserted or particles may be blown. An electrical connection should be provided for automatically grounding the meter element to the connecting box (metal wire housing) if a connecting box is provided. The base should be highly weather-resistant since many of the bases will be exposed to salty atmosphere near the ocean. The various standard connections must be possible and, in fact, the connecting facilities should preferably be standard. Lightness in weight is desirable to reduce shipping costs. It is highly desirable that the terminals to which the wires are connected be insulated from one another with non-tracking insulating material. With some insulating materials, such as .Balrelite, there is danger that under abnormal circumstances a conductive path or track will be formed on the surface of the insulating material, and if this happensa current flowing along the track will increase. the conductivity of the track and more and more current will pass until there may even be an explosion.

A base similar to that illustrated in Holmes Patent No. 2,046,307 has seen extensive use and is the most satisfactory which has been provided it is especially satisfactory when a porcelain terminal block, already available, is used therein. This Holmes base was made of cast aluminum. Inview of the present abnormal demand for aluminum, it is desirable to provide a base which is not made of aluminum but which has the above mentioned qualities nevertheless.

According to the present invention, a porcelain meter base with a terminal combined therewith has been provided. This base has nearly all the advantages of the Holmes aluminum base except that itis a little heavier. It is not nearly as heavy as a cast iron or steel base would be. In addition, it has other advantages, such as the fact that it is largely made up of a non-trackable insulating material which makes it safer than previous meter bases and permits the integral incorporation of the terminal block therein. It also is extremely hard to drill. A number of detailed problems had to be solved to provide this base, but they have all been solved satisfactorily.

Although a major object of the invention was to provide a satisfactory base not made of aluminum or like metal, an additional'obiect was to solve the various specific problems involved in the provision of a porcelain base.

Further objects and advantages of the invention will be apparent, from the following description and from the drawings, in which:

Fig. l is an exploded perspective view showing the main porcelain body portion and separated therefrom most of the parts which are applied to this body portion to complete the base.

Fig. 2 is a similar view showing the rear and bottom of the body portion together with some of the parts removed from the back thereof.

Fig. 3 is a fragmentary cross sectional view taken approximately on the line 33 of Fig. 1.

Fig. 4 is a perspective view of the cover-securing insert shown cemented to the base in Fig. 3.

Fig. 5 is a somewhat diagrammatic view illustrating the manner of obtaining accurate positioning of the insert with respect to the body portion of the base as the insert is cemented thereto.

Fig. 6 is a fragmentary face view of the portion of the base which forms the terminal block showing wires connected thereto.

Fig. l is a bottom view of the base.

Fig. 8 is a generally horizontal sectional view taken approximately on the irregular line 8-8 of Fig. 6.

Fig. 9 is a similar view taken approximately on the irregular line 9-4? of Fig. 6.

Fig. 10 is a fragmentary vertical sectional view taken approximately on the line l0lll of Fig. 6.

Fig. 11 is a generally vertical sectional view taken approximately on the line ll-ll of Fig. 1.

Figs. 12 and 13 are generally vertical'sectional views taken approximately on the lines l2l2 and lt-l 3, respectively, of Fig. 6.

Fig. 14 is a generally vertical sectional view taken approximately on the irregular line 14-14 of Fig. 1, broken away to show the break-out wall Ill.

Fig. 15 is a fragmentary partly sectional view taken approximately on the irregular line l5-l 5 of Fig. 6.

Fig. 16 is a fragmentary partly sect onal view taken approximately on the irregular line l6-l 6 (ill of Fig. 1.

A preferred form of the invention has been chosen for illustration and description, in compliance with section 4888 of the Revised Statutes, but persons skilled in the art will readily perceive other means for accomplishing the same results, and the claims are therefore to be construed as broadly as possible, consistent with the prior art.

The body portion ll of this form of the invention is seen best in Fig. 1. This body portion is preferably porcelain molded inone piece. A dry process porcelain is preferred for reasons of economy and because there is less shrinkage than with the wet process. Any type of porcelain whichcan be suitably molded and which will not deteriorate by exposure to weather even under the most adverse conditions, such as alternate rain and freeze, may be used. A typical formula would be: feldspar 36%, pctters flint 24%, Tennessee ball clay Georgia kaolin 10%, Florida kaolin 8%, and tale 2%. Composition of such porcelain body may be varied by substitut'ons and additions of such material as pyrophyllite, dolomite and, to produce a gray body, not over 6% of iron chromate. The materials are preferably air-floated.

This body portion may be made of other plastics, such as glass or the non-ceramic plastics of which Bakelite is an example. Glass is d'mcult, if not impossible, to mold in the com plicated shape shown, however, and the ceramic Mounting features It is desirable to provide the base with standard mounting facilities. For this purpose it is desired to provide a keyhole hanger l2 on the back of the meter near its top, this hanger being reversible to put either end up according to the wishes of the particular power supply company install ng the meter. To obtain this reversibility in the most desirable and standard form it is necessary to secure the hanger l2 to the base of the meter by a screw l3 passing through hole [4 in the hanger which must be at theexact position shown best in Fig. 14. It so happens, however, that the standard meter measuring element for which this base is designed is secured to the base by three mounting lugs of which one is the upper lug I6, shown in Fig. 14. Space requirements necessitate the positioning of this mounting lug It as shown in Fig. 14, and it will be noted that the hole through this mounting lug is out of alinement with the hole I4 in the hanger l2.

It will be understood that the various screws cannot be threaded into the porcelain since the porcelain threads would chip off and would not hold the screws reliably and are difficult and expensive to form. Accordingly, metal portions must be provided for the screw l3 and the measuring element mounting screw I8 and, as previously noted, the two metal portions must in this case have their tapped holes slightly out of alinement.

It is believed that in this instance the misalined tapped holes are best provided by the two plates 2| and 22, seen best in Figs. 1, 14 and 16. These plates 2| and 22 are both drawn tight onto the body portion II by means of screws 23 which are passed from the back of the base through plate 22 and screwed into plate 2|. A yielding sealing gasket 25 could be used under plate 22, the material known as Velutex being at present preferred.

The base II is provided with a suitable thickened portion 24 for properl positioning the plate 2| and a suitable recess 26 for receiving the plate 22 and the hanger l2. It is also provided with passages 21 for receiving screws 23 and with recesses 28 for receiving screws 13 and Hi.

In order that the base may be mounted on a slightly uneven wall without placing excessive strain on the porcelain body portion, the hanger I2 is arranged to project slightly rearwardly from the body portion so as to hold the body portion slightly spaced from the wall. It is likewise desirable that the lower end of the porcelain body portion be held slightly spaced from the wall, and for this reason the mounting means at the bottom of the body portion, namely the plate 3|, is also arranged to project rearwardly beyond the body portion. As a matter of fact, it has been shown as being positioned entirely behind a flush surface of the bod portion, th s being done because a fiat surface is preferred in order to facilitate supporting the entire body portion while it is being fired. If a recess were provided for the plate 3| and the lower end not supported, the lower end might sag and cause excessive irregularities of shape. The plate 3| should be of a thickness corresponding to the projection of hanger l2 behind body portion preferably about 1 inch, so as to support the body portion H in vertical position. The interal parts will; of course, be dimensional to hold the measuring element in proper position rela tive to the body portion The bottom mounting plate 3| is best seen in Figs. 1, 10 and 15. This plate is secured against the back of the body portion II by means of two screws 32. As indicated in Fig. 1 and as seen in Fig. 10, one of the screws 32 passes through the plate 3|, then through a hole 33 in the procelain, and screws into a metal block 34, having a second purpose described under the heading Terminal chamber cover. The 0: screw 32, as indicated in Fig. 1 and as seen in Fig. 15, passes through the plate 3|, then through another hole 33 in the porcelain, through a sealing plate 36, and threads into a metal block 31. The plate 3| is also provided with holes 39 through which mounting screws for the base may be passed to screw into the wall against which the base is mounted.

The measuring element is provided with one mounting lug 4|, shown in dotted lines in Fig. 14, on each side thereof. Each of these lugs is secured by a screw 42 which passes through the lug and is threaded into a bushing 43. As seen best in Fig. 11, each bushing 43 is provided with an elongated portion 44 threaded at both ends, into one of which a screw 46 is threaded to draw the bushing 43 tight against the body portion II or, more specifically, against a yielding sealing gasket 41. It will be observed that both the screws 42 and 48 can screw into opposite ends of a single tapped bore of portion 44, as shown in Fig. 11. However, the construction shown in Fig. 3 is preferred, the solid center portion of the bushing positively preventing the seepage of moisture along the threads. In Fig. 11, the head of screw 46 bears on grounding strap 48 which is described under the heading Grounding connection. As indicated in Figs. 1 and 3, the head of screw 46 at the other side of the meter bears against a washer 49.

Accurate positioning of parts Since porcelain is not fired in the mold, there are minute variations between successive body portions molded from the same mold, these variations resulting from differences in shrinkage or the like. It is very desirable, however, that the asetgess for mounting measuring element be accurately and uaiicrmly positioned with respect 1 providing oversiaed. holes a these husli ags tor the bushings may he positioned with I through to avoid.

connection heretofore m nufacture 11a}: stra; T) having a bins -ale thereattao :rrent coil of "*l mayta do "more he positioned in a .hcely portion eel l screw will screw the uprece- .16 hole o the nut c' "he cal strap is also provided with he the screw to which may he screw, heals against a i'table by handle til to 1" one: or to be spaced also link under the potential mom ininal strap U5 (Figs. 6 and 12) is fastened. A

spacer it is provided on screw a l so that the as sociatecl terminal unit will have a little play to facilitate allnement of the terminal unit with relatively inflexible connections, but such play is not necessary tor he parts associated. with screw 68.

meter will ordinarily be provided with two terminal units comprising the straps ii and terminal member it will also ordinarily be pro viclecl with four of the main terminal units although, as seen in Fig. 6, two of them will be longer the other two.

The terminal units are inserted by removing the screws therefrom, slipping them up into the body portion, and inserting the screws through appropriate holes in the front of the body portion. lfl'lese screws, once screwed into the terminal clamp hold the terminal clamp in place.

It is not desirable to have the bottoms of the terminal units exposed, as this might result in accidental shocks and might invite tampering. According to the present invention, the terminal units are shielded from the bottom by a guard plate 173 formed of suitable insulating material. Porcelain could be used. for this, but accurate measurements are desirable and furthermore the plate is relatively thin and long so that, if made one another. This is preferably accomplished v irecl. The screw threads into Gil the flange: 6; the chances c Acellte) by de .t with the e edges se. ce w. res set outwardly crtions o5 ter" lit, the rear edge clown iroi 1 plate ll If the ire is at, it will usually be bent forwardly, and it y ll be ohsei that there is much more room between nd the forward edge oi e orward edge is spaced iv 'irclly of the normal position of the g screw is seen from the side edges i l of the wire-receiving are spaced. anart more widely than the inside op line of terminal clamp and each is set heel: the inside plane thereof. The plate I designed to have a slight clearance (T le. ill with the porcelain all around and may be provided with lugs l5 fitting beside spa oially provided lugs iii (Fig, 12) on the body portion, hath of which are so disposed that the guard plate can only be applied in one position it right side up. Lugs it can be omitted in the interests of simplification or the guard plate it is symmetrical so that its position is immaterial. The lugs l5 also decrease the likelihood of tracking as do the grooves l9, by increasing the surface distances between conductors, ac= cording to principles taught in Patent 2,154,412 issued jointly to Stanley S. Green and me. In the case of lug E5 the surface distance increased is that along the top of the plate "l3 between voltby lateral flanges ll on brackets 16 welded to washers ll which are welded to the mounting plate 3!. All of these parts may be spot welded together simultaneously. These brackets 18 may engage flanges 18 formed integrally on the ends of the guard plate 13. The brackets 18 are preferably somewhat curved or angular in cross section so as to increase their rigidity and so as to conform in shape to standardization requirements.

Washers 11' are provided, and are flattened on their undersides, so as not to interrupt channel 88 into which lip 8| of the connecting box may extend as seen in Fig. 11. It is desirable that the connecting box be externally overlapped from above wherever there is no other sealing, to prevent water from running into the connecting box.

Meter cover It is highly desirable that the meter base be adapted to have standard covers mounted thereon so that these covers may be interchangeable between the new base and old bases. Heretofore these covers have been secured by three, bayonet clamps which, upon slightly turning the cover, slide under lugs formed on the base in the position of the lug 8| shown in Fig. 3. By turning the cover, the resilient bayonet arm of the clamp draws the cover tight against a sealing rib such as the rib 82 in Fig. 3. This arrangement is disclosed in the Holmes Patent No. 2,046,307 mentioned heretofore. A porcelain lug in place of the lug 8| would not have adequate strength for securing the cover. According to the present invention, therefore, the lug 8| is formed as part of a metal insert or slug 83 cemented in a recess or passage 84 in the body portion I I. covers require three of the lugs 8|, one of the inserts 83 is thus cemented in each of the three recesses 84 seen in Fig. 1.

In order for the bayonet clamp to act properly, it is necessary for the lugs 8| to be positioned accurately with respect to the sealing rib 82, a tolerance of only .005 inch in either direction being permissible according to one manufacturer's standards. To provide this accuracy, the sealing rib 82 is first ground to a plane. It should be noted, incidentally, that the provision of the narrow sealing rib 82 not only aids in having a high contact sealing pressure with the cover gasket but also greatly reduces the cost of grinding the sealing surface to flatness, since the slight amounts necessary to be ground from the narrow sealing rib 82 may be ground oif quite inexpensively. The grinding of the sealing rib is considered necessary, first because the finished porcelain is not always uniform, and second because a fiber gasket is preferred to a rubber gasket since a rubber gasket might stick or more or less vulcanize itself to the cover and to the rib and prevent twisting the cover to loosen the bayonet clamps.

After grinding the sealing rib 82 to a plane, the three inserts 83 are secured to a jig represented more or less diagrammatically by 88, and the body portion H is slipped over them so that each insert 83 extends into the recess 84, as seen two members are positioned with respect to each other with extreme accuracy. Any suitable cement 88 is now poured into the recess 84, and the parts are left on the jig until the cement has hardened sufficiently to make removal of the Since the body portion Ii with the inserts 83 therein safe. The cement 88 may be any suitable ceramic cement, preferably of low shrinkage characteristics. Of course, it must be waterproof. Litharge and glycerin cement or Portland cement are also possibilities. A type metal may also be considered as a suitable cement, since it has the desirable characteristic of expanding on cooling so that it is sure to hold the insert 83 firmly.

The described method of mounting the inserts 83 in the base has the additional advantage that it places the inserts properly with respect to one another so that they define a circle of predetermined diameter appropriate for proper cooperation with the cover. In other words, the fact that the base may have shrunk will not cause these lugs to be so improperly positioned that there will be objectionable lateral play of the cover.

The insert 83 may be made of any suitable strong metal, the strongest and most n0n-corrosive consistent with price considerations being preferred. Among others, both the silicon bronze known as Everdur and red brass are suitable. The insert 83 is preferably shaped so as to facilitate the flow of the cement around it while, at the same time presenting an irregular shape which increases the safety with which it is anchored. It may not only be irregular longitudinally but it may be provided with the notches 89, seen best in Fig. 4.

Terminal chamber cover The region in which the terminal clamps 58 are located has heretofore been called the terminal chamber, and for convenience this term may still be used. Since a separate terminal block has been provided heretofore, the base has in past been formed with this whole zone vacant to leave room for the terminal block. According to the present invention, however, it is understood that the insulating portions of the terminal block are an integral part of the body portion. It is nevertheless necessary to provide a metal cover for the terminal chamber to prevent accidental shocks or tampering on the part of unauthorized persons. For the sake of interchangeability, it is again desirable that standard terminal chamber covers fit the new base. To this end the securing formations for the standard terminal chamber cover 90 must be provided intheir usual positions. As seen in Figs. 1 and 10, the block 34 into which the screw 32 is screwed for securing the back plate 3| is provided with a button 8| at the proper position for engaging s, keyhole slot in a conventional terminal chamber cover 90. A hexagonal nut welded to a plate having a rivet thereon may be preferable from the manufacturing standpoint. At the other end of the terminal chamber a link 82 is slidably secured above the terminal chamber, being secured as best seen in Fig. 15 by means of a bracket 83 which may be secured to the body portion by a rivet 94. The inner end 86 of the slidable link 82 is passed inwardly (to the left) against a lug on the bottom of the cover 90 after the cover has been turned clockwise to tighten the bayonet clamps. This method of locking the main cover is in accordance with standard practice, except that the method of securing the sliding link 92 is new. When the link 92. is in its inner locking position, the sealing plate 88 (Figs. 1 andv 15)" extends through a slot 88 in the slidable link 92. The terminal chamber cover 98 may now be closedWith the lug accuses the front ends of these This effectively p'tevents prying the ts downwardly obtain access to a screw M92. "it migh be noted that t i to provide porce 1e cg" the brackets stud cc l to t is. to be formed witi.

terminal blocl; portion of the on ii is provided w a thin sealing it is not necessary grind this to a gas c (Fig. 11) may be used. Possible vulcanization of the rubber at this point does not -t a serious danger since the terminal c-.. mber cover ild may easily be pried off even if the "rubber should vulcanize.

Sometimes a dlfrereutmeans of securing the initial chamber cover is provided by a par ticular power supply organization, this means comprising bolts screwed through the cover into meter base. To accommodate these bolts, tapped holes Hill are provided. According to the present invention, these tapped holes provided at substantially no es ra cost by position ing the screws for the support plate Si so that the tapped holes into which they screw are in the correct positions to receive the COVGf-SGCllI- tug bolts. In other words, the screws of course screw only about half way through the blocks 36 and til or less leaving the remainder oi the tapped holes lol for the cover-securing bolts. lihese bolts are of course suitably sealed, as by a rod extending through the bolts and sealed this position.

Additional connections For some circuits it is desirable to have one or tw extra voltage connections leading into the meter, besides the connections provided through the four main terminal units to. For this purpose, drilling recesses Hill are provided in the guard plate it, the position of these being shown in Fig. 'l. The inner end of this recess may be drilled out very easily to permit a wire iii to pass therethrough as shown in dotted lines in Figs. 6 and 12. The porcelain body portion is provided with a passage M2 through which this wire may extend to thevoltage con hector till, being held therein by a screw lit which may be inserted through the face of the terminal block portion of the body member. A like passage is provided at the other end of the terminal chamber portion of the body member. Of course, when a feed wire IN is used, the disconnect link 66 and its associated screws will be omitted. Likewise, when a'wire corresponding to wire I]! is extended through the till other drilling recess Hill, the discor illil and its associated screws will b Besides the facilities for the two taken through'the recesses desirable to provide ccnnectio' s n devices in connection wit de this purpose, three additi i i are provided in the hotto it, as. seen. in Fig. Who these recesses are drill out sible a passage lit through ing wires may extend into u. c

thin wall ill is preferably 12 L fracture, but it can easily be bro-hem. o passage is to be used. it may b insulating wall is r "ired hetwe ter terminal units betwe sage is provided because both connected i voltage di erential esirnal voltag Goundiug 1.

.iccoi'ding to best wir tions and like metal poi. iueut should be connect it a meter tester shou' as by standing on a v nations and one of the c "is wrapp d this grounding of the automatically whencve: was used for housing meter. This resulted 1" meter unit was mounts metal lugs and the metal. frame w s mounted in contact with the connection be be conventionally grounded. Although obvious advantages in halting the of insulating material accorda ce a1 invention, this insulating materia to care of the automatic grounding Oi. meter unit. According to the present invention, how

ever, this failure is overcome with complete satisfaction by providing the grounding strap it.

seen best in Figs. 2 and ii. This grounding strap is connected to the laminations of meter unit by virtue of lying under the head of one of the screws is holding one of the bosses bushings lit in place. It should he understood that the mounting lug ll on the meter unit is made of metal and is in direct contact with the lamina tions.

)fhe grounding strap is connected to ground by being in contact with the mounting plate ill which will automatically be placed in electrical contact with the connecting box in mountin the meter. The connecting box is represented in 11 by the member i2l which may be a bracket or extension on the back of a connecting box against which the meter base is clamped by the mounting screw Hit.

It should be observed that, as shown at H22: in Fig. 2 and in dotted lines in Fig. 11, the grounding strap 38 may be shaped with its lower end curled up slightly, the curling being exag gerated in the drawings. When the mounting plate Si is tightened against the grounding strap it by crews 32 this curltwill be more or less straightened out and the grounding strap placed under stresswhich presses the upturned end into firm contact with the mounting plate 35. This ensures a good grounding connection. At the present time welding of the ground strap to the mounting plate 3| is preferred to the spring conta ct shown.

The grounding strap 48 should be made of some weather-resistant material, such as galvanized iron. It may be noted, incidentally, that all of the metal parts are preferably protected from excessive corrosion either by composition or by plating.

Antitampering features The provision of the guardplate 13 and the manner of securing it has already been described, as has the fact that the securing brackets 16 therefor prevent access to the mounting screws I02. The lip I21 and the blocking plate I29 have also been described. The double wall of the Holmes Patent No. 2,046,307 has not been provided, but porcelain is so diflicult to drill that this double wall is not believed to be necessary. Furthermore, the use of a single wall which is sufficiently difficult to drill so that a double wall is not necessary provides more room within the main meter chamber for the meter element or with Fig. 5. With the illustrated form it will probably be desirable next to apply the members to which the meter element is mounted. In applying plate 2|, the plate 22 will of course be applied. While applying one of the bushings 43, the grounding strap 48 will be applied. Next, the four nuts 62 will be inserted, after which the four terminal units 56 will be slipped up into place from the bottom of the body portion, and the screws 59 inserted through the front to hold them in place. At this time the voltage terminal units 69, II will also be inserted from the bottom, and whichever screws will be used therewith inserted from the front. The guard plate I3 may now be 5 applied, after which the mounting plate ill will be put in place and drawn tight by screws 32. The sliding link 92 may be applied by riveting the bracket 93 to the body portion at any time.

In case the grounding strap is welded to mount- 0 ing plate 3| the bushings '43' will probably be apfor accessories thereto, and makes possible the 25 provision of a relatively smooth back wall which is easily wiped clean. It may be noted in this connection that if a, portion of the meter winding i quite close to the base, there is no danger of spark-overs because the base itself is formed of insulating material.

To minimize the danger that someone will attempt to pry up the cover with a screw driver, the outer wall of the meter base which comes almost into contact with the cover is beveled as seen at I24 in Fig. 14. The cover should come close enough to the inner end of the bevel so that there will not be room for a screw driver to be inserted between it and the cover, and the beveled portion itself will not provide a suitable purchase or fulcrum for prying with the screw driver.

Formation of the body portion The body portion is of a shape which can be molded in accordance with known molding practices, although it may be advantageous to point out certain special features. No attempt has been made to illustrate a taper or draft for facilitating removal of the molds or cores, but this may be provided wherever desired.

Molding the slots for the terminal straps 51 may present a special problem since a core approximately the shape of these straps might be flexed under the molding pressures. To overcome this danger, these cores may be thickened through most of their length, thus forming the cavity I26, seen for example in Fig. 13. The lip I21 at the upper end of this cavity should be left so as to minimize the possibility of insertion of wires into the meter chamber by meter tamperers. Of course, if desired, the upperend of terminal clamp 58 can also be obstructed by applying a plate I29 thereto as the connecting unit 56 is insertedinto the body portion. Although this plate has been shown as formed of insulation, it could be formed of metal and, incidentally, could be formed as an integral part of the terminal strap 51 or terminal clamp 58.

Assembly For the most part the assembly is apparent from the foregoing description. Of course, the inserts 83 for securing the main cover will probably be applied first, as described in connection plied last.

From the foregoing it is seen that a combined meter base and terminal block is provided which is completely non-conductive except where metal parts are desired, which is so completely immune to corrosion or other changes upon exposure to even the most corrosive atmospheres that it does not need to be painted, and which is almost drillproof and tamper-proof' Furthermore, it conforms with existing bases in all respects in which standardization is desirable, particularly as to the covers and meter units which fit it. It provides more space within the meter chamber than any previous base which was as hard to drill into. Although it is not as light as an aluminum base. it is considerably lighter than a cast iron base. In spite of these advantages. it is economical in cost and may even prove to be capable of manufacture at a lower cost than any previous high quality base and terminal block assemblies.

I claim:

1. A base for watt-hour meters and the like, comprising an insulating body portion formed of a ceramic, having slots extending inwardly from the outside thereof, terminal units positioned in said slots and secured therein by binding screws, said body p rtion having integral ceramic walls insulating some of said terminal units one from another, and a guard plate, of a plastic less brittle than the ceramic, outside of the terminal units and slightly spaced therefrom by an air gap to prevent tracking between the terminal units along the guard plate if the guard plate is trackable.

2. A base for watt-hour meters and the like,

,, comprising an insulating body portion formed of a fired ceramic, having a narrow sealing rib for engaging a cover, having recesses adjacent the sealing rib, and having irregularly shaped metallic inserts cemented in the recesses, each insert having a lug extending therefrom in a direction to engage a bayonet clamp to secur the cover to the base, the recesses being oversize with respect to the inserts and the inserts being accurately positioned with respect to each other and the sealing-rib independently of shrinkage or warping in firing the base.

3. A base for watt-hour meters and the like. comprising an insulating body portion formed of a fired ceramic, having a narrow sealing rib for engaging a cover, having recesses adjacent the sealing rib, and having metallic inserts cemented in the recesses, each insert having a lug extending therefrom in a direction to engage a bayonet clamp to secure the cover to the base, the recesses being oversize with respect to the inserts and the inserts being accurately positioned with respect to each other and the sealingrib independently of therein by binding screws and some of which are positioned in closely spaced side by side relationship but are insulated from one another by a wall of the plastic integral with the body portion.

5. A base for watt-hour meters and the like, comprising an insulating body portion formed of a ceramic, having slots extending inwardly from the outside thereof, and terminal units positioned in said slots and secured therein by binding screws, said body portion having integral ceramic walls insulating some of said terminal units one from another and an integral front wall through which the terminal-screws pass but which shield said units from the front.

- 6 A base for watt-hour'meter's and the like, comprising an insulating body portion formed of a plastic, having passage means extending inwardly from the outside thereof, terminal units secured in said passage means positioned within the ends of the passage means and surrounded by the body except for their end faces, and an insulating guard plate mounted outside of the terminal units.

7. A base for watt-hour meters and the like, comprising an insulating body portion formed of a plastic, having passage. means extending inwardly from the outside'thereof, terminal units secured in said passage means, and an insulating guard plate mounted outside of the terminal units,

, said insulating guard plate having conductor-receiving openings therethrough, the edges of which are spaced slightly outwardly from alinement with the conductor-engaging portions of the terminal units whereby conductors passing through the portion for mounting the base to a wall, said mounting plate securing said guard plate in position and being positioned to engage a conventional connecting box for wires leading to the measuring unit, and said metallic means including said mounting plate being in contact with the metallic insert for grounding the measuring unit.

11. The method of making a base for watthour meters and the like, which consists in providing a preformed body portion of insulating material, having a sealing surface lying approximately in a plane and adapted for the sealing of a cover thereagainst, and having a plurality of pockets adjacent said surface but variably positioned with respect thereto because of the forming process, temporarily securing three widely spaced lugged metallic inserts in said pockets with the lugs thereon adapted to engage bayonet cover clamps and positioned accurately with respect to said plane and in relation to one another but independently of their positions in said pockets, and permanently securing said inserts to said base while thus. temporarily secured by putting cement in said pockets around said inserts.

- 12. A base for watt-hour meters and the like comprisinga ceramic body portion forming, in part at least, a terminal chamber and a meter chamber and having slots extending inwardly through the terminal chamber and into the meter chamber from the outside of the body, terminal units positioned in said slots, secured therein by 'binding screws and having a terminal strap porits cross section is substantially filled by the terguard plate are unlikely to contact the guard plate.

8. A base for watt-hour meters and the like, having terminal units positioned therein and extending inwardly from an outer wall thereof, and an insulating guard plate mounted outside-the terminal units, said insulating guard plate having conductor-receiving openings therethrough, the edges of which are spaced away slightly from alinement with the conductor-engaging portions of the terminal units,whereby conductors passing through the guard plate are unlikely to contact the guard plate.

9. A base for watt-hour meters and the like, comprising an insulating body portion formed of a plastic, having a metal mounting plate secured to the back portion of the body portion, a guard member of insulation secured on the outside of the base by saidmounting plate, and terminal units within the base protected by said guard vmember.

10. A base for watt-hour meters an the lik comprising a body portion formed of insulating material forming a measuring unit chamber and a terminal portion, a metallic insert for mounting the measuring unit in themeasuring unit chambergan insulating guard plate positioned outside of the terminal-portion, and metallic means including a mounting plate secured to the body anism therein comprising three minal strap. said body portion having integral ceramic walls insulating some of said terminal units, one from another, and a guard plate formed of a plastic less brittle than the ceramic but of trackable characteristics secured outside of the terminal units, substantially covering the ends thereof exposed at the ends of the slots but slightly spaced therefrom by an air gap to prevent tracking between the terminal units along the guard plate, said guard plates having holes through which conductors pass to the terminal units, the walls of said holes being slightly spaced away from the position which would contact a straight conductor clamped in the terminal units whereby the danger of tracking across the guard plate between conductors is minimized.

13. A meter base for watt-hour meters and the like comprising a ceramic body portion which has been fired, and means for mounting a meter mechindependent I members each adapted to receive a mounting screw for the mechanism, and each independently secured in a hole by means passing through the body of the base whereby a plane is defined, even if there is warpage in the base for receiving the measuring element with three-point mounting, at least two of the holes being'oversize with respect to the means therein whereby the members may be spaced accurately with respect to one another irrespective of slight dimensional variations in the body portion, the front side of the body portion being free from obstructions along central areas thereof to provide the maximum depth for receiving the measuring element.

- RICHARD A. ROAD. 

